Terminal construction for fuses and the like



March 20, 1 951 s. LINDELL 2,546,074

TERMINAL CONSTRUCTION FOR FUSES AND THE LIKE Filed June 2, 1949 Patented Mar. 20, 1951 TERMINAL CONSTRUCTION FOR FUSES AND THE LIKE Sigurd I. Lindell, Chicago, 111., assignor to S & Electric Company, Chicago, 111., a corporation of Delaware Application J une 2, 1949, Serial No. 96,652

15 Claims. 1

This invention relates generally to electric fuses, and it has particular relation to the construction and assembly of the terminals or ferrules at the ends of tubular fuse housings or the like.

Among the objects of this invention are: To avoid the use 'of solder in interconnecting the end terminals or ferrules at the ends of a fuse housing and the conductor within the same which includes a fusible section; to interlock the ferrules and the .fuse housing at each end of the latter; to close the ends of the fuse housing in such manner as to resist internal stress resulting from high pressure created on blowing of the fusible section; to employ :an inner and an outer ferrule as each end of the housing with knurling to provide intimate electrical and mechanical engagement therebetween without requiring close tolerances; to locate the knurling externally on each inner ferrule for mechanically engaging the fuse housing to prevent relative turning; and to construct the various parts so that the fuse assembly can be readily and economically manufactured.

Other objects of this invention will, in part, be obvious and in part appear hereinafter.

This invention is disclosed in the embodiment thereof shown in the accompanying drawing and it comprises the features of construction, combination of elements and arran ement of parts which will be exemplified in the construction hereinafter set forth and the scope of the application of which will be indicated in the appended claims.

For a more complete understanding of the nature and 'scope of this invention, reference may be had to the following detailed description, taken together with the accompanying drawing, in which:

- Figure 1 is a longitudinal sectional View of a {use construction in which the present invention is embodied;

'Fi'gure 2 'is a view, partly in side elevation and partly in section, of one of the inner ferrules;

Figure '3 is an end 'view of the ferrule shown in Figure '2;

Figure 4 is 'a view, in end elevation, of the inner ferrule for the other end of the fuse tube; and

Figure is 'a view, partly in side elevation and partly in section of the other inner ferrule shown in Figure 4.

Referring now to the drawing, it will be ob served that the reference character l0 designates, generally, a fuse device certain portions of which are illustrated and described in Lindell Patent No. 2,323,229 issued June 29, 1943, and assigned to the assign'ee of this application. The fuse device It] includes a tubular fuse housing ll of suitable insulating material such as fibre. Its ends 12 and I3 are reduced in diameter for receiving outer ferrules l4 and l5, respectively, which are formed of hard drawn copper tubing. The ends 1-2 and I3 are cut away an extent equal to the thickness of the walls of the ferrules l4 and l 5 so that their outer diameter is the same as the outer diameter of the intermediate portion of the tubular fuse housing '1. .Itwill be noted that annular grooves l6 and I! are prov ded intermediate the cut away end surfaces I2 and [3 for receiving radially inwardly extending ribs 1 8 and [9 which are formed after the ferrules H! and 15 are ositioned on the ends of the tubular fuse housing I! by suitable deformin means such as rolling dies. It will be noted also that the end portions 20 and 2| of the ferrules l4 and it are reduced in diameter and that the ends 22 and '23 are closed. This con truction together with the ribs in and 19 rolled into the grooves l9 and I1 provides an assemb y which is ca able of resistin the stresses usua ly set up within the housing II when the fuse b ows.

Within the left hand end of the t bular fuse hous n' H. as vie ed'in Figure 1 there is a cupsh o d nner ferrule 26 that is formed nreferably of ha d drawn copper, Its construction is illustrated in more detail in Figures 9.. and 3. It has an inner small diameter portion 21 which, as sho n n Fi ure l. inte fits with the adiac nt end of the tub lar fuse ho sing l-l. A so it has an o t di me e po tion 28 ru h is ewternally iongit dinallv kn rl d as indicated at 29. An annular sho l e 3'1 is pro ded bet een the Fortions 21 and 28 and it is arranged to bear against a cor es ondin annular shoulder 3| at the inner end of a rec ss d inner end surface 32 of the "tubular fuse ho sing I l The externa ly longitudinal y knurled porton 29 on the inner ferrule 26 cooperates with the tubular fuse housing II and the outer ferrule II to prevent relative turnin 'thereb'etween. It'will be noted that the inner portion 33 of the knurling 29 is coextensive with the recessed inner end surface 32 and that this knurled portion bites into this surface so that intimate mechanical engagement therewith is obtained. This is accomplished'by havin the outer diameter of the portion 28 of the ferrule 26 slightly larger than the inner diameter of the recessed inner end surface 32 and then forcing the ferrule 26 into position so that its shoulder 30 engages the shoulder 3i.

Thereafter the outer ferrule id is forced into place and, since the inner diameter of the end portion 2!) of the outer ferrule M is slightly less than the external diameter of the portion 28 of the inner ferrule 25, both electrical and mechan ical engagement is provided therebetween. The line contact provided by the knurled portion insures a low electrical resistance joint between the ferrule 26 and is without requiring the use of solder. At the same time intimate mechanical engagement between these parts prevents the outer ferrule Hi from turning with respect to the inner ferrule 26.

The outer ferrules is and i are interconnected by a conductor which includes a fusible section. One end 3? of this conductor which includes a flexible conductor 38 extends through openings 39 and All, Figure in the bottom of the inner ferrule 26 and is positioned, as shown in Figure 1, between the outer end of the inner ferrule and the end portion 20. The construction is such that this end 3! of the flexible conductor 38 is both mechanically and electrically engaged under pressure between these parts and thus the desired electrical contact therewith is provided. Flexible conductor 38 extends over a. pulley M which is rotatably mounted on an arm 12 at one end of a tension spring 43 which is carr ed by a shaft M that extends transver ely of the ferrule 26 through bearing openings 45 in recessed portions 46 therein. The other end l? of the tension spring 43 bears against the inner end of the inner ferrule 25 as shown more clearly in Fi ure 1. The pulley M and tension spring as are provided for tensioning the conductor 35 in the manner described in the aforesaid Lin ell patent.

It will be ob erved that the flexible conductor 38 extends from the inner ferrule 2 throu h central opening 50 in the bottom thereof into a bore 5! of a block 52 of arc extingui hing material such as boric acid. The flexible conductor 38 is connected by a terminal sleeve 53 to one end of a fusible section 54 in the form of a strain wire. It will be understood that the fusible s ction 54 is calibrated to blow under certain time and current conditions which need not be described in detail here. The other end of the fusible section 56 extends into a. termin l 55 which has an intermediate flange 56 that bears against a washer 51 which is located at the inner end of the block 52 of arc extinguishing Inaterial. It will be understood that thetens on spring 43 is restrained by the flange 56 hearin again t the washer 51 through the conn ct on thereto by the flexible conductor 38 and the fusible section 5 In this manner the block 52 of arc extinguishing material is placed in compression.

Within the tubular fuse housing I! and beyond the block 52 of arc extinguish ng material there is a resistor 58 which is in the form of a coil of hard drawn tungsten wire. One end of the resistor 53 is connected to the termin l 55. The resistor 58 is embedded in a filling 59 of marble dust and its other end is connect d to terminal 60. The functioning of the resistor 58 formed of a coil of tungsten wire with the marble dust filling 59 and the interaction thereof with the fusible section 54 are described in detail in the aforesaid Lindell patent and will not be repeated here.

It will be observed that the terminal 6! which is identical in construction with the terminal 55,

extends through an opening 6! in a central recessed portion 62 of an inner ferrule 63 which is shown more clearly in Figures 4 and 5 of the rawings. The inner ferrule 63 preferably is formed of hard drawn copper and its inner edge 54 bears against an annular shoulder 65 of the tubular fuse housing Ii. The annular shoulder 55 is located at the inner end of a recessed inner end surface 55 of the tubular fuse housing H which is coextensive with the inner portion 6'! of external longitudinal knurling 68 on the inner ferrule 63. L ke the inner ferrule 26 described above, the outer diameter of the inner ferrule 63 is somewhat larger than the diameter of the inner end surface 56 so that, when the inner ferrule 53 is forced into the end of the tubular fuse housing l i, the knurled portion El bites into the surface 66 and is thereby held against turning. The outer portion 69 of the longitudinal knurling 68 has intimate electrical and mechanical engagement with the inner surface of the reduced di ameter end portion 2% of the outer ferrule 55 This not only provides electrical connection be tween these parts without requiring the use of solder but also it provides intimate mechanical engagement so as to prevent relative turning.

The outer end of the terminal 60 is headed over as indicated at it so as to hold it in posit-ion on the inner ferrule 53 and to provide good mecha'n ical and electrical connection thereto. Openings H are provided in the inner ferrule 63 to permit the entrance of the marble dust filling 59 after assembly and prior to application of the outer ferrule 55. In assembling the fuse device ill, the fusible section is first joined to one end of the flexible conductor 38 by the terminal sleeve 53. The lat-f ter is deformed onto the ends of these elements; Thereafter, the resistor 58 with the terminals 55 and 6B deformed onto its ends is aligned with the fusible section 50, and one end of the termi nal is defor ed onto its free end. Next the tension spring 43 and the ulley M are assembled within the inner ferrule 26. the spring. being carried by the shaft 44. The previously asseme bled flexible conductor 38 and t e fu ible section 54 are threaded through the washer H and the block 52 of arc extingu shing material which is located adiacent the inner ferrule 25. The flexihle conductor 23 is t readed throu h the op ning 58 in the bottom of the ferrule 25. around the pulley ll, which may be held in the position shown in Figure .1 by s ecial tool. through the openings 40 and and the end 31 t en is hooked over the out r end of the inner ferrul 36. When the s ec al tool is removed t e s ring 43 places the fusible section 5 3 in ten ion and the block 52 of are extinguishing material in compression.

The arts assembled as just described are positioned in the tubular fuse housing H through the left hand end and the inner ferrule 25 is forced inwardly until its annu ar sh ulder 30 engages the annular shoulder 39. Thereafter the terminal 5!! is pulled out of the oth r end of the tubular fuse housing l! and the other inner ferrule 69 is secured thereto by the h aded over portion 10. After this has been done the inner ferru e 53 is forced into the right hand end of the tubular fuse housing H until its inner edge 6!! enga es the shoulder 65. I No the external ferrule M is forced over the left hand end of the tubular fuse housing I I acumen closes the left hand end of the tubular iuse housing II.

The space :around the resistor :58 within the tubular 'fusehousing I I :now is filled with marble dust 59 through the openings II in the inner ferrule 63. Thereafter the outer ferrule I is forced over the right hand end l3 of the tubular .fuse housing 'I with which it has a press fit until its reduced diameter end portion 2,! engages the end of the fuse housing I I. Finally both of the outer ferrules HI and I5 are deformed by rolling to prowide the radially inwardly extending ribs I8 and 1 9 which project into the annular grooves I16 and I1, respectively, so as to hold the :ferrule assemblies at the ends .of the tubular fuse housing II from endwise movement.

It will be noted that the ends of the fibre fuse housing II are positioned between the inner portions 33and B1 of the inner ferrules 26 and 53 and the outerferrules It and 15. This construction insures that theends of the housing I i can notexpand on absorbin moisture and move away from the inner ferrules 26 and 63 since these portions thereof are held incompression.

When the knurled construction is employed for the inner ferrules 26 and 53, as described, it is unnecessary to hold the tolerances of these ferrules and the outer ferrules l4 and I5 as close as would otherwise be required if the knurling were omitted and reliance were placed on merely a press fit therebetween. This materially reduces the cost of manufacture and, at the same time, increases the speed of assembly. The longitudinal knurling bites into the end surfaces 32 and 66 and also into the inner surfaces of the end portions and 2! of the outer ferrules I 4 and I5.

Multiple line contact under pressure is established by the knurled surfaces 29 and 68 of the inner ferrules 2e and 53 with the smooth inher surfaces of the outer ferrules M and I5 with which they have a press fit. If desired, the outer cylindrical surfaces of the inner ferrules 2B and 63 can be smooth and the inner cylindrical surfaces of the outer ferrules I4 and i5 can be knurled to provide the intimate mechanical and electrical engagement therebetween and the mechanical engagement with the ends of the housing Ii.

Since certain changes can be made in the foregoing construction and different embodiments of the invention can be made without departing from the spirit and scope thereof, it is intended that all matter shown in the accompanying drawing and described hereinbefore shall be interpreted 'as illustrative and not in a limiting sense.

What is claimed as new is:

1. In a fuse construction, in. combination, a tubular insulating housing, an externally longitudinally knurled inner ferrule extending into each end of said housing with the longitudinal knurling biting into the inner end surface of said housing and extending beyond the ends thereof, a conductor including a fusible section extending through said housing and electrically interconnecting said inner ferrules, and an outer ferrule telescoped over each end of said housing, the outer end portion of each outer ferrule being reduced in diameter so that the longitudinal lrnurling on each inner ferrule bites into the innersurfa-ce of the outer 'ferrule,'the longitudinally knurled portions of said inner ferrules providing intimate electrical and mechanical engagement between them and the outer ferrules and intimate mechanical engagement between them and said housing whereby the electrical resistance at the joint between each inner and outer ferrule is reduced and both ferrules at each end are prevented from turning relative to :each other and to said housing.

2. The invention, asset forth in claim 1, wherein "one end of the conductor is positioned between one inner ferrule and the corresponding outer ferrule and is mechanically gripped thereby to provide a low electrical resistance therebetween.

23. The invention, as set forth in claim 2, wherein a terminal is provided on the other end of the conductor and it is secured by deformation to the other inner ferrule.

4. In a fuse construction, in combination, a tubular insulating housing, .an externally longitudinally knurled inner ferrule extending into each end of said housing with the longitudinal knurling biting into the inner end surface of said housing and extending beyond the ends thereof, a conductor including a fusible section extending through said housing and electrically interconnecting said inner ferrules, and an outer ferrule closed at one end and telescoped over each end of said housing, the closed end portion of each outer ferrule being reduced in diameter so that the longitudinal knurling on each inner ferrule bites into the inner surface of the outer ferrule, the longitudinally knurled portions of said inner ferrules providing intimate electrical and me chanical engagement between them and the outer ferrules and intimate mechanical engagement between them and said housing whereby the electrical resistance at the joint between each inner and outer ferrule is reduced and both ferrules at each end are prevented from turning relative to each other and to said housing.

5. In a fuse construction, in combination, a tubular insulating housing with the inner portion of each end recessed to provide an annular shoulder, an externally longitudinally knurled inner ferrule extending into each end of said housing and bearing against the shoulder thereat with the longitudinal knurling biting into the inner end surface of said housing and extending beyond the ends thereof, a conductor including a fusible section extending through said housing and electrically interconnecting said inner ferrules, and an outer ferrule closed at one end and telescoped over each end of said housing, the closed end portion of each outer ferrule being reduced in diameter so that the longitudinal knurling on each inner ferrule bites into the inner surface of the outer ferrule, the longitudinally knurled portions of said inner ferrules providing intimate electrical and mechanical engagement between them and the outer ferrules and intimate mechanical engagement between them and said housing whereby the electrical resistance at the "joint between each inner and outer ferrule is reduced and both ferrules at each end are prevented from turning relative to each other and to said housing.

In a fuse construction, in combination, a tubular insulating housing with the inner portion of each end recessed to provide an annular shoulder and having an external annular groove near each end, an externally knurled inner ferrule extending into each end of said housin and bearing against the shoulder thereat with the knurling biting into the inner end surface of said "housing and extending beyond the ends thereof, a conductor including a fusible section extending through said housing and electrically interconnecting said inner ferrules, and an outer ferrule closed at one end and telescoped over each end of said housing and having a radially inwardly extending rib interfitting with said annular groove thereat, the closed end portion of each outer ferrule being reduced in diameter so that the knurling on each inner ferrule bites into the inner surface of the outer ferrule, the knurled portions of said inner ferrules providing intimate electrical and mechanical engagement between them and the outer ferrules and intimate mechanical engagement between them and said housing whereby the electrical resistance at the joint between each inner end and outer ferrule is reduced and both ferrules at each end are prevented from turning relative to each other and to said housing.

'7. In a fuse construction, in combination, a tubular insulating housing with the inner portion of each end recessed to provide an annular shoulder and having an external annular groove near each end, an externally knurled inner ferrule extending into each end of said housing and bearing against the shoulder thereat with the knurling biting into the inner end surface of said housing and extending beyond the ends thereof,

a conductor including a fusible section extending through said housing and electrically interconnecting said inner ferrules, and an outer ferrule closed at one end and telescoped over each end of said housing and having a radially inwardly extending rib groove thereat, the closed end portion of each outer ferrule being reduced in diameter so that the knurling on each inner ferrule bites into the inner surface of the outer ferrule, the knurled portions of said inner ferrules providin intimate electrical and mechanical engagement between them and the outer ferrules and intimate mechanical engagement between them and said housing whereby the electrical resistance at the joint between each inner and outer ferrule is reduced and both ferrules at each end are prevented from turning relative to each other and to said housing, the end portions of said housing being reduced an amount corresponding to the thickness of each outer ferrule whereby the external diameter thereof is the same as that of the intermediate portion of said housing.

8. In a fuse construction, in combination, a tubular insulating housing, an externally longitudinally knurled inner ferrule extending into one end of said housing with the longitudinal knurling biting into the inner end surface and extending beyond said end thereof, a conductor including a fusible section extending through said housing and electrically connected to said inner ferrule, and an outer ferrule telescoped over said end of said housing, the outer end portion of said outer ferrule being reduced in diameter so that the longitudinal knurling on said inner ferrule bites into the inner surface thereof, the longitudinal knurled portion of said inner ferrule providing intimate electrical and mechanical engagement between it and said outer ferrule and intimate mechanical engagement between it and said housing whereby the electrical resistance at the joint between said inner and outer ferrules is reduced and both ferrules are prevented from turning relative to each other and to said housing.

9. The invention, as set forth in claim 8, Wherein one end of the conductor is positioned between the ferrules and is mechanically gripped thereby to provide a low electrical resistance therebetween.

10. The invention, as set forth in claim 8, wherein a terminal is providedon one end of the interfitting with said annular 8 conductor and it is secured by deformation to the inner ferrule.

11. In a fuse construction, in combination, a tubular insulating housing, an externally longitudinally knurled inner ferrule extending into one end of said housing with the longitudinal knurling biting into the inner end surface and extending beyond said end thereof, a conductor including a fusible section extending through said housing and electrically connected to said inner ferrule, and an outer ferrule closed at one end and telescoped over said end of said housing, the closed end portion of said outer ferrule being reduced in diameter so that the longitudinal knurling on said inner ferrule bites into the inner surface thereof, the longitudinally knurled portion of said inner ferrule providing intimate electrical and mechanical engagement between it and said outer ferrule and intimate mechanical engagemen between it and said housing whereby the electrical resistance at the joint between said inner and outer ferrule is reduced and both ferrules are prevented from turning relative to each other and to said housing.

12. In a fuse construction, in combination, a tubular insulating housing with the inner portion of one end recessed to provide an annular shoulder, an externally longitudinally knurled inner ferrule extending into said end of said housing and bearing against said shoulder with the longitudinal knurling biting into the inner end surface and extending beyond said end thereof, a conductor including a fusible section extending through. said, housing and electrically con' nected to said inner ferrule, and an outer ferrule closed at one end and telescoped over said end of said housing, the closed end portion of said outer ferrl le being reduced in diameter so that the longitudinal knurling on said inner ferrule bites into the inner surface thereof, the longitudinally knurled portion of said inner ferrule providing intimate electrical and mechanical engagement between it and said outer ferrule and intimate mechanical engagement between it and said housing whereby the electrical resistance at the joint between said inner and outer ferrules is reduced and both ferrules are prevented from turning relative to each other and to said housing.

13. In a fuse construction, in combination, a tubular insulating housing with the inner portion of one end recessed to provide an annular shoulder and having an external annular groove near said end, an externally knurled inner ferrule extending into said end of said housing and bearing against said shoulder with the knurling biting into the inner end surface and extending beyond said end thereof, a conductor including a fusible section extending through said housing and electrically connected to said inner ferrule, and an outer ferrule closed at one end and telescoped over said end of said housng and having a radially inwardly extending rib interfitting with said annular groove, the closed end portion of said outer ferrule being reduced in diameter so that the knurling on said inner ferrule bites into the inner surface thereof, the knurled portion of said inner ferrule providing intimate electrical and mechanical engagement between it and said outer ferrule and intimate mechanical engagement between it and said housing whereby the electrical resistance at the joint between said inner and outer ferrules is reduced and both ferrules are prevented from turning relative to each other and to said housing.

,14. In a fuse construction, in combination, a

tubular insulating housing with the inner portion of one end recessed to provide an annular shoulder and having an external annular groove near said end, an externally knurled inner ferrule extending into said end of said housing and bearing against said shoulder with the knurling biting into the inner end surface and extending beyond said end thereof, a conductor including a fusible section extending through said housing and electrically connected to said inner ferrule, and an outer ferrule closed at one end and telescoped over said end of said housing and having a radially inwardly extending rib interfitting with said annular groove, the closed end portion of said outer ferrule being reduced in diameter so that the knurling on said inner ferrule bites into the inner surface thereof, the knurled portion of said inner ferrule providing intimate electrical and mechanical engagement between it and said outer ferrule and intimate mechanical engagement between it and said housing whereby the electrical resistance at the joint between said inner and outer ferrules is reduced and both ferrules are prevented from turning relative to each other and to said housing, the end portion of said housing being reduced an amount corresponding to the thickness of said outer ferrule whereby the external diameter thereof is the same as that of the intermediate portion of said housing.

15. In a fuse construction, in combination, a tubular insulating housing, an inner ferrule extending into each end of said housing with a portion extending beyond the ends thereof, a conductor including a fusible section extending through said housing and electrically interconnecting said inner ferrules, and an outer ferrule telescoped over and having a press fit with each end of said housing and the inner ferrule thereat, the outer end portion of each outer ferrule being reduced in diameter, one of the juxtaposed surfaces of the ferrules at each end of said housing being longitudinally knurled thereby providing intimate electrical and mechanical engagement between them and intimate mechanical engagement with said housing whereby the electrical resistance at the joint between each inner and outer ferrule is reduced and both ferrules at each end are prevented from turning relative to each other and to said housing.

SIGURD I. LINDELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,502,883 Sandin July 20, 1924 1,517,981 Grieve Dec. 2, 1924 1,540,000 Glowacki June 2, 1925 1,907,740 Clark May 9, 1933 2,108,550 Rawlins Feb. 15, 1938 2,416,428 Boothe Feb. 25, 1947 

